added initial code that can help support canvas tooltips for observer widgets

coretk/coretk/canvastooltip.py

@@ -0,0 +1,134 @@
+import tkinter as tk
+from tkinter import ttk
+
+
+class CanvasTooltip:
+    """
+    It creates a tooltip for a given canvas tag or id as the mouse is
+    above it.
+
+    This class has been derived from the original Tooltip class updated
+    and posted back to StackOverflow at the following link:
+
+    https://stackoverflow.com/questions/3221956/
+           what-is-the-simplest-way-to-make-tooltips-in-tkinter/
+           41079350#41079350
+
+    Alberto Vassena on 2016.12.10.
+    """
+
+    def __init__(
+        self,
+        canvas,
+        tag_or_id,
+        *,
+        bg="#FFFFEA",
+        pad=(5, 3, 5, 3),
+        text="canvas info",
+        waittime=400,
+        wraplength=250
+    ):
+        # in miliseconds, originally 500
+        self.waittime = waittime
+        # in pixels, originally 180
+        self.wraplength = wraplength
+        self.canvas = canvas
+        self.text = text
+        self.canvas.tag_bind(tag_or_id, "<Enter>", self.on_enter)
+        self.canvas.tag_bind(tag_or_id, "<Leave>", self.on_leave)
+        self.canvas.tag_bind(tag_or_id, "<ButtonPress>", self.on_leave)
+        self.bg = bg
+        self.pad = pad
+        self.id = None
+        self.tw = None
+
+    def on_enter(self, event=None):
+        self.schedule()
+
+    def on_leave(self, event=None):
+        self.unschedule()
+        self.hide()
+
+    def schedule(self):
+        self.unschedule()
+        self.id = self.canvas.after(self.waittime, self.show)
+
+    def unschedule(self):
+        id_ = self.id
+        self.id = None
+        if id_:
+            self.canvas.after_cancel(id_)
+
+    def show(self, event=None):
+        def tip_pos_calculator(canvas, label, *, tip_delta=(10, 5), pad=(5, 3, 5, 3)):
+
+            c = canvas
+
+            s_width, s_height = c.winfo_screenwidth(), c.winfo_screenheight()
+
+            width, height = (
+                pad[0] + label.winfo_reqwidth() + pad[2],
+                pad[1] + label.winfo_reqheight() + pad[3],
+            )
+
+            mouse_x, mouse_y = c.winfo_pointerxy()
+
+            x1, y1 = mouse_x + tip_delta[0], mouse_y + tip_delta[1]
+            x2, y2 = x1 + width, y1 + height
+
+            x_delta = x2 - s_width
+            if x_delta < 0:
+                x_delta = 0
+            y_delta = y2 - s_height
+            if y_delta < 0:
+                y_delta = 0
+
+            offscreen = (x_delta, y_delta) != (0, 0)
+
+            if offscreen:
+
+                if x_delta:
+                    x1 = mouse_x - tip_delta[0] - width
+
+                if y_delta:
+                    y1 = mouse_y - tip_delta[1] - height
+
+            offscreen_again = y1 < 0  # out on the top
+
+            if offscreen_again:
+                y1 = 0
+
+            return x1, y1
+
+        bg = self.bg
+        pad = self.pad
+        canvas = self.canvas
+
+        # creates a toplevel window
+        self.tw = tk.Toplevel(canvas.master)
+
+        # Leaves only the label and removes the app window
+        self.tw.wm_overrideredirect(True)
+
+        win = tk.Frame(self.tw, background=bg, borderwidth=0)
+        label = ttk.Label(
+            win,
+            text=self.text,
+            justify=tk.LEFT,
+            background=bg,
+            relief=tk.SOLID,
+            borderwidth=0,
+            wraplength=self.wraplength,
+        )
+
+        label.grid(padx=(pad[0], pad[2]), pady=(pad[1], pad[3]), sticky=tk.NSEW)
+        win.grid()
+
+        x, y = tip_pos_calculator(canvas, label)
+
+        self.tw.wm_geometry("+%d+%d" % (x, y))
+
+    def hide(self):
+        if self.tw:
+            self.tw.destroy()
+        self.tw = None

coretk/coretk/graph.py

@@ -4,6 +4,7 @@ import tkinter as tk
 
 from core.api.grpc import core_pb2
 from coretk.canvasaction import CanvasAction
+from coretk.canvastooltip import CanvasTooltip
 from coretk.graph_helper import GraphHelper, WlanAntennaManager
 from coretk.images import Images
 from coretk.interface import Interface
@@ -512,6 +513,7 @@ class CanvasNode:
         self.canvas.tag_bind(self.id, "<Button-3>", self.context)
         self.canvas.tag_bind(self.id, "<Double-Button-1>", self.double_click)
         self.canvas.tag_bind(self.id, "<Control-1>", self.select_multiple)
+        self.tooltip = CanvasTooltip(self.canvas, self.id, text=self.name)
 
         self.edges = set()
         self.wlans = []